This study seeks to determine if a co-ordinated assembly of pre-existing and newly synthesized chromosomal proteins exists in the replication of nuclear chromatin that might help explain how nucleo-protein complexes in the parental molecule are faithfully copied in the daughter molecules. Nascent chromatin will be isolated and the order of assembly will be monitored. In addition, "repaired chromatin" will be isolated to determine if newly synthesized chromosomal proteins are assembled onto segments of DNA that have been damaged by known carcinogens and that have been repaired by the excision-repair mechanism.